The relationship between muscle activation during gait and cartilage volume loss in patients with non-traumatic and post-traumatic knee osteoarthritis

Abstract

Purpose: Gait measures have been shown to relate to disease progression in patients with knee osteoarthritis (OA). For instance, higher co-contraction of medial knee muscles during gait was related to medial tibial cartilage loss over 12 months in patients with knee OA; higher co-contraction of the lateral knee muscles was protective against cartilage loss. Differences in muscle activation during gait have been found between patients with non-traumatic (i.e. no previous traumatic injury) and post-traumatic (i.e. history of previous trauma) knee OA. Patients with non-traumatic OA had higher quadriceps activation and prolonged lateral hamstring activation compared to patients with post-traumatic knee OA. Considering these differences, the relationship between disease progression and muscle activation might also vary between these knee OA subtypes. Therefore, the objective was to explore relationships between muscle activation during gait and cartilage volume loss over 2 years in patients with non-traumatic and post-traumatic knee OA. Methods: Participants with non-traumatic (n=14) and post-traumatic (n=10) knee OA were recruited. This latter group had a history of anterior cruciate ligament rupture confirmed on magnetic resonance imaging (MRI). Muscle activation of vastus lateralis, vastus medialis, lateral hamstrings, and medial hamstrings were recorded with surface electromyography (EMG) as participants completed five gait trials at self-selected speeds. Ensemble averages were created from the five trials and gait EMG were normalized to maximum voluntary isometric contractions. Principal component analysis determined important characteristics (principal components) from EMG waveforms and individual participant waveforms were scored against these principal components (PC-scores). Cartilage volume was measured with a 3.0T MRI with a knee coil, and scans were completed on two occasions separated by 2 years. The sequence was a T1-weighted, 3D sagittal gradient echo sequence with fat suppression. The change in cartilage volume over 2 years was determined with an automatic procedure in the medial and lateral knee compartments (Medical Imaging, ArthroLab Inc., Montreal, Quebec, Canada). Pearson correlations between PC-scores from gait EMG and cartilage volume change were calculated separately for non-traumatic and post-traumatic OA groups. Results: Both higher lateral hamstring activation (PC1; r=0.59, p=0.03) and higher vastus lateralis activation during terminal stance/early swing (PC2; r=0.57, p=0.03) were significantly related to less medial compartment cartilage volume loss in the non-traumatic OA group. Also, earlier onset of vastus lateralis activation (PC3) was related to greater medial compartment cartilage volume loss in the non-traumatic OA group (r=-0.65, p=0.01). There were no significant correlations between muscle EMG and cartilage volume loss in the post-traumatic OA group and no significant correlations in the lateral compartment for both groups (Table 1). Conclusions: Higher activation of the lateral hamstrings and vastus lateralis during gait were protective against medial compartment cartilage loss in participants with non-traumatic knee OA. These muscle activation patterns might represent an attempt to unload the medial compartment, although there is inconsistency in the literature if this truly occurs. Earlier onset of vastus lateralis led to increased medial compartment cartilage loss in the non-traumatic OA group. This muscle might not be at peak activation when maximum joint loads typically occur and thus is not adequately controlling joint loading. There were no significant findings in the post-traumatic OA group. Thus, the role of muscle function in OA progression likely varies between patients with non-traumatic and post-traumatic knee OA. Long term studies with larger study samples are required to further examine the relationship between muscle function and disease progression in these OA subtypes.Tabled 1Table 1 Correlations (r) between EMG PC-scores and cartilage volume loss.MusclePrincipal ComponentNon-traumatic OAPost-traumatic OALateral CompartmentMedial CompartmentLateral CompartmentMedial CompartmentVastus Lateralis1-0.110.450.030.2320.250.570.320.143-0.01-0.650.35-0.34Vastus Medialis1-0.030.440.020.2220.170.400.440.193-0.21-0.340.40-0.05Lateral Hamstrings10.210.59-0.41-0.0320.030.390.280.4230.03-0.29-0.570.18Medial Hamstrings10.100.37-0.22-0.322-0.050.420.30-0.3130.110.15-0.450.06 Open table in a new tab